1. Configuration verification: A missing link toward fully verified networks Ratul Mahajan Microsoft Research With: Ari Fogel, Stanley Fung, Ramesh Govindan, Todd Millstein, Luis Pedrosa, Meg Walraed-Sullivan

2. Networks are unreliable Unreliability is expensive

3. (An old) vision

4. But what does it mean? Hardware Forwarding software Data plane state Router runtime Configuration

5. Why configuration (verification) is hard? Low-level, per-device configuration Multiple routing protocols Redistribution across protocols Access control and isolation n1 n2 n3 C P p1 c1 c2 10.0.0.0/24 2.2.2.0/24 3.3.3.0/24 n4 N

6. Approaches for configuration analysis Data plane state Router runtime Configuration

7. Batfish n1 n2 n3 C P p1 c1 c2 10.0.0.0/24 2.2.2.0/24 3.3.3.0/24 n4 N [A generalized approach to network configuration analysis, NSDI 2015]

8. Demo

9. Results on two university networks PS. Wrt the prefix that was dual-assigned from yesterday, one of my NOC guys stopped by today to ask what voodoo I was using to find such things - Email from the head of the Net1 NOC

10. Implications It is possible to build a declarative model of existing networks – Can aid transition to SDNs – Can capture network management activity across time – Can capture network’s computation and its complexity https://github.com/arifogel/batfish

11. Toward fully verified networks ? Hardware Forwarding software Data plane state Router runtime Configuration Management plane Data plane computation …. Protocol interactions